Plants Of Different Ages Research Articles

Micropropagation of Ficus religiosa L. via leaf explants and comparative evaluation of acetylcholinesterase inhibitory activity in the micropropagated and conventionally grown plants.

A high-frequency, season-independent, in vitro regeneration of Ficusreligiosa was developed, followed by comparative acetylcholinesterase inhibitory (AChEI) activity assay of the in vitro raised and conventionally grown plants. The use of AChEI activity is the most accepted strategy for the treatment of Alzheimer disease. Fully expanded, mature leaves were cut into different segments to initiate the cultures. The middle section of the leaf in vertical orientation with cut portion inserted inside the medium was found most suitable for direct shoot regeneration. Leaf explants responded with nearly consistent frequency (60–66.67 %) throughout the year. To obtain high frequency response with enhanced shoot multiplication rate, 32 plant growth regulator regimes were screened amongst which benzylaminopurine at 5.0 mg/l was found most suitable, yielding 100 % response and maximum number of shoots per explant (7.93); same concentration was also most supportive for repeated multiplication (6.53 shoots). The quality of the shoots and multiplication rate could be significantly enhanced (24.35 shoots) when adenine sulphate, glutamine and phloroglucinol, in an optimised concentration, were additionally supplemented. The clonal nature of the micropropagated plants was confirmed by random amplified polymorphic DNA analysis. A comparative analysis of AChEI activity was carried out amongst the methanolic extracts of stem segments of the mother plant, randomly selected seedlings of different age (4 and 6 months old) of the same mother plant and randomly selected micropropagated plants of different age (3 and 6 months age). The mother plant sample showed effective AChEI activity, with IC50 of 66.46 μg/ml while seedlings, of different age groups, performed poorly (6-month-old seedlings, Se-16M, yielded IC50 of 20,538.46 μg/ml, while two randomly selected 4 months’ aged seedlings, Se-24M and Se-34M exhibited IC50 of 19,341.03 and 24,281.70 μg/ml). On the other hand, various micropropagated plants, 2 of 3 months (MiP-13M, MiP-23M) and 2 of 6 months (MiP-36M and MiP-46M) age behaved like the mother plant, exhibiting IC50 values of 71.87, 72.91, 67.65 and 69.65 μg/ml, respectively.

First Report of Bacterial Wilt Caused by Ralstonia solanacearum on Roselle in Taiwan.

Roselle (Hibiscus sabdariffa L.) is a herbaceous plant belonging to the Malvaceae family. Its calyxes are rich in vitamin C and anthocyanins and are used to make roselle drink and hibiscus tea. Roselles are grown in counties of Taitung, Pingtung, and Chiayi in Taiwan. In addition to a few local cultivars, the major cultivar currently grown in Taiwan is Roselle cv. Victor. In April of 2012, a wilt disease appeared on seedlings of a cultivar, Chiada 1, at the Chungpu Township of Chiayi County. Mature plants were free from this disease. Leaves appeared weak and drooping when they were still green, followed by collapse of the whole plant a few days later. Browning of vascular and pith tissues was evident, especially at the base of the stem. A whitish mass of bacteria oozed from the cut end of diseased stems, suggesting that bacteria might be the cause of this disease. A total of 15 bacterial strains were collected. Colonies on tetrazolium chloride medium (3) were round to oval and fluidal, each with a pink or red center after incubation at 30°C for 48 h. When tobacco leaves were infiltrated with these strains, a hypersensitive reaction (HR) typical of phytopathogenic bacteria was induced. All strains produced the expected amplicon (282 bp) after PCR with the Ralstonia solanacearum-specific primer pair, AU759f and AU760r (4). Three hexose alcohols (mannitol, sorbitol, and dulcitol), rather than three disaccharides (lactose, maltose, and cellobiose), were utilized, which suggests R. solanacearum biovar 4 (2). R. solanacearum phylotype I was determined by phylotype-specific multiplex PCR (1). Pathogenicity of the strains was tested on roselle, tomato, pepper, and eggplant. Young plants of the various species were inoculated at the four- to six-leaf stage by soil drenching with 30 ml of bacterial suspension (about 108 CFU/ml). Control plants were inoculated with sterile water. Each treatment comprised eight plants with a single plant in each pot. Plants were incubated in a greenhouse at 25 to 31°C and 56 to 93% humidity. Wilting was observed 4 to 6 days after inoculation, while the control did not wilt. To find the correlation between plant growth stage and resistance to the pathogen, 2-, 3-, 4-, and 5-week-old roselle plants cv. Chiada 1 were transplanted into artificially infested soil. Eight plants in each treatment were planted with a single plant in each pot. The disease incidences for plants of different ages were 75%, 62.5%, 50%, and 12.5%, respectively. This study showed that resistance increases with plant age. Hence, if older seedlings are transplanted, the risk of bacterial wilt of roselle can be reduced. To our knowledge, this is the first report of R. solanacearum on roselle in Taiwan.

Physiological Effects of Squash vein yellowing virus Infection on Watermelon.

Squash vein yellowing virus (SqVYV) is the cause of viral watermelon vine decline. The virus is whitefly-transmitted, induces a systemic wilt of watermelon plants, and causes necrosis and discoloration of the fruit rind. In the field, SqVYV is often detected in watermelon in mixed infections with other viruses including the aphid-transmitted Papaya ringspot virus type W (PRSV-W). In this study, watermelon plants of different ages were inoculated with SqVYV or SqVYV+PRSV-W in the greenhouse or SqVYV in the field to characterize the physiological response to infection. Symptoms of vine decline appeared about 12 to 16 days after inoculation with SqVYV regardless of plant age at time of inoculation, plant growth habit (trellised or nontrellised), and location (greenhouse or field). However, the presence of PRSV-W delayed the appearance of vine decline symptoms by 2 to 4 days, and vine decline did not develop on plants with no fruit. For all inoculation treatments, more severe symptoms were observed in younger watermelon plants. Physiological responses to SqVYV infection included reduction in plant and fruit weights, alterations in fruit rind and flesh color, reduction in fruit sucrose content, increase in fruit acid content, and changes in plant nutrient composition, particularly increases in Ca, Mg, B, Mn, and Zn and decreases in K and N. These results demonstrate wide-ranging physiological effects of SqVYV infection and provide new insights into watermelon vine decline.

Mycorrhiza for all: an under‐earth revolution

Mycorrhiza for all: an under‐earth revolution

Patterns in δ15N in roots, stems, and leaves of sugar maple and American beech seedlings, saplings, and mature trees

Stable isotopes of nitrogen (N) in plants are increasingly used to evaluate ecosystem N cycling patterns. A basic assumption in this research is that plant d 15 N reflects the d 15 N of the N source. Recent evidence suggests that plants may fractionate on uptake, transport, or transformation of N. If the dominant source of plant N is via roots, a difference in d 15 N by tissue type would suggest fractionation on transport and assimilation of N. In order to evaluate differences between species and plant parts, we measured d 15 N in root, stem, and leaf tissues of individual sugar maple (Acer saccharum; SM) and American beech (Fagus grandifolia; BE) plants ranging in age from germinants to mature trees at the Hubbard Brook Experimental Forest, New Hamp- shire (USA). For SM, root d 15 N ( stem d 15 N ( leaf d 15 N; for BE seedlings, root d 15 N ( stem d 15 N and root d 15 N ( leaf d 15 N. These differences suggest that fractionation occurs during plant transport and assim- ilation of N. Beech d 15 N (root, stem, and leaf) was consistently higher than SM d 15 N for 1-7 year-old seedlings. At one site, we found no differences with age in foliar d 15 N (range: 4.1-4.8 %) for seedlings, saplings, and trees which suggests that it may be possible to compare foliar d 15 N of plants of different ages at some sites. However, at another site, foliar and root d 15 N were higher for trees than 1-2 year-old seedlings. This study suggests that physiological differences in N assimilation and transport processes that differ by species likely control plant d 15 N.

Selection of Reference Genes for Quantitative Gene Expression Studies in Platycladus orientalis (Cupressaceae) Using Real-Time PCR

Platycladus orientalis is a tree species that is highly resistant, widely adaptable, and long-lived, with lifespans of even thousands of years. To explore the mechanisms underlying these characteristics, gene expressions have been investigated at the transcriptome level by RNA-seq combined with a digital gene expression (DGE) technique. So, it is crucial to have a reliable set of reference genes to normalize the expressions of genes in P. orientalis under various conditions using the most accurate and sensitive method of quantitative real-time PCR (qRT-PCR). In this study, we selected 10 reference gene candidates from transcriptome data of P. orientalis, and examined their expression profiles by qRT-PCR using 29 different samples of P. orientalis, which were collected from plants of different ages, different tissues, and plants subjected to different treatments including cold, heat, salinity, polyethylene glycol (PEG), and abscisic acid (ABA). Three analytical software packages (geNorm, Bestkeeper, and NormFinder) were used to assess the stability of gene expression. The results showed that ubiquitin-conjugating enzyme E2 (UBC) and alpha-tubulin (aTUB) were the optimum pair of reference genes at all developmental stages and under all stress conditions. ACT7 was the most stable gene across different tissues and cold-treated samples, while UBQ was the most stably expressed reference gene for NaCl- and ABA-treated samples. In parallel, aTUB and UBC were used singly or in combination as reference genes to examine the expression levels of NAC (a homolog of AtNAC2) in plants subjected to various treatments with qRT-PCR. The results further proved the reliability of the two selected reference genes. Our study will benefit future research on the expression of genes in response to stress/senescence in P. orientalis and other members of the Cupressaceae.

Recombinant monoclonal antibody yield in transgenic tobacco plants is affected by the wounding response via an ethylene dependent mechanism

Variability in recombinant IgG yield in transgenic tobacco plants has previously been observed in relation to leaf position, and is interpreted as a function of ageing and the senescence process, leading to increasing protein degradation. Here, similar findings are demonstrated in plants of different ages, expressing IgG but not IgG-HDEL, an antibody form that accumulates within the endoplasmic reticulum. Antibody yields declined following wounding in young transgenic plants expressing IgG but not in those expressing IgG-HDEL. However, in mature IgG plants, the opposite was demonstrated, with significant boosts in yield, while mature IgG-HDEL plants could not be boosted. The lack of response in IgG-HDEL plants suggests that the changes induced by wounding occur post-translationally, and the findings might be explained by wounding responses that differ in plants according to their developmental stages. Plant mechanisms involved in senescence and wounding overlap to a significant degree and compounds such as ethylene, jasmonic acid and salicylic acid are important for mediating downstream effects. Treatment of transgenic plants with ethylene also resulted in a decrease in recombinant IgG yield, which was consistent with the finding that wounded plants could induce lower IgG yields in neighbouring non-wounded plants. Treatment with 1-MCP, an ethylene antagonist, abrogated the IgG yield drop that resulted from wounding, but had no effect on the more gradual IgG yield loss associated with increasing plant age.

Organogênese direta de Orthophytum mucugense

Orthophytum mucugense é uma bromélia ornamental endêmica do município de Mucugê-BA que está passível de extinção. O objetivo deste trabalho foi estabelecer um protocolo de regeneração via organogênese direta para a espécie. Os explantes raiz, caule e folha, oriundos de plantas com diferentes idades, foram inoculados em meio de cultura MS½ suplementado com BAP e ANA. Os brotos foram inoculados em meio contendo AIB e carvão ativo. As plantas foram transferidas para substrato composto de vermiculita e terra. A maior taxa de brotação foi obtida com o explante caule com 20 e 40 dias de idade em meio com 0,65mM de ANA. Na fase de enraizamento, a presença de carvão ativo interferiu positivamente no comprimento da parte aérea e do sistema radicular das plantas. As plantas foram aclimatizadas com 100% de sobrevivência.

PLANT AGE AND STRAIN OF RALSTONIA SOLANACEARUM AFFECT THE EXPRESSION OF RESISTANCE OF TOBACCO CULTIVARS TO GRANVILLE WILT

Granville wilt (GW), a devastating disease of tobacco, is best managed through a combination of rotation with nonhost crops, soil fumigation, and implementation of resistant cultivars. Resistance incorporated from Nicotiana tabacum T.I.448A has been the source of resistance against GW in the United States. Resistance is hard to select for and deployment is difficult as location specificity exists for different races and biovars of GW worldwide. Various methods of determining cultivar resistance to GW in tobacco have been utilized with the use of plants of different ages and various strains of Ralstonia solanacearum. In this study we modified a laboratory method previously developed for determining races of Phytophthora nicotianae and examined its effectiveness to evaluate cultivars for resistance to GW. Two root injury methods, root abrasion and root wounding, were tested with 16 strains collected from tobacco fields in North Carolina in 2008. Four cultivars were used: K 346, SP 168, NC 71, and K 326. Res...

Seasonal Abundance of the Nearctic Gall MidgeObolodiplosis robiniaein Italy and the Impact of Its AntagonistPlatygaster robiniaeon Pest Populations

AbstractThe Nearctic gall midge Obolodiplosis robiniae (Haldeman, 1847) (Diptera Cecidomyiidae) infesting black locusts, Robinia pseudoacacia L. (Fabaceae), was detected in Asia in 2002 and in Europe (first in Italy) in 2003. Its distribution in Europe has expanded dramatically, probably favored by extensive distribution of its host plant along the main routes. The results of a 3-yr study on the seasonal abundance of O. robiniae in northern Italy are reported here. O. robiniae can develop three to four generations per year by exploiting plants of different ages and vigor. Overwintering takes place as diapausing larvae and adults emerge in spring. Two generations are completed on mature plants where populations decline in summer. Two additional generations can develop on root suckers from midsummer onward. Pest population densities reach their highest levels in late spring. Gall midge larvae were attacked by various predators, but parasitism by the platygastrid Platygaster robiniae Buhl & Duso was particularly significant. The impact of parasitism by P. robiniae is indicated as a key factor in reducing O. robiniae population densities.

Sexual dimorphism in resource acquisition and deployment: both size and timing matter.

The males and females of many dioecious plant species differ from one another in important life-history traits, such as their size. If male and female reproductive functions draw on different resources, for example, one should expect males and females to display different allocation strategies as they grow. Importantly, these strategies may differ not only between the two sexes, but also between plants of different age and therefore size. Results are presented from an experiment that asks whether males and females of Mercurialis annua, an annual plant with indeterminate growth, differ over time in their allocation of two potentially limiting resources (carbon and nitrogen) to vegetative (below- and above-ground) and reproductive tissues. Comparisons were made of the temporal patterns of biomass allocation to shoots, roots and reproduction and the nitrogen content in the leaves between the sexes of M. annua by harvesting plants of each sex after growth over different periods of time. Males and females differed in their temporal patterns of allocation. Males allocated more to reproduction than females at early stages, but this trend was reversed at later stages. Importantly, males allocated proportionally more of their biomass towards roots at later stages, but the roots of females were larger in absolute terms. The study points to the important role played by both the timing of resource deployment and the relative versus absolute sizes of the sinks and sources in sexual dimorphism of an annual plant.

Rapid plant regeneration, analysis of genetic fidelity and essential aromatic oil content of micropropagated plants of Patchouli, Pogostemon cablin (Blanco) Benth. – An industrially important aromatic plant

Rapid and prolific shoot regeneration via direct organogenesis was induced from leaf explants of Patchouli, Pogostemon cablin (Blanco) Benth., an aromatic plant of immense industrial value, on Murashige and Skoog (MS) medium with benzylaminopurine (BAP) and α-naphthaleneacetic acid (NAA) within 4 weeks. The adventitious shoot bud induction and plant regeneration were greatly influenced by the origin, age of donor plant, and leaf position on stem. Leaf explants prepared from in vivo plants of different ages showed higher regeneration response as compared to the explants from in vitro plantlets of respective age. The shoot regeneration ability of explants was significantly related to the age of the donor plants as well as the leaf position on the stem. The highest number of shoots (94.6/explants) was obtained from 96.2% of leaf explants derived from the leaves located on the second node of the 3-month-old in vivo plants on Murashige and Skoog's (MS) medium containing 2.5 μM benzylaminopurine (BAP) and 0.5 μM naphthaleneacetic acid (NAA). Incorporation of 1.0 μM gibberellic acid (GA 3) in MS medium significantly improved the shoot elongation (1.8-fold) within 2 weeks in 95% of the cultures. Regenerated shoots rooted spontaneously on growth regulator-free half strength MS medium and were successfully hardened and transferred to nursery with 96–100% survival rate. Genetic fidelity of the in vitro derived plants was assessed using random amplified polymorphic DNA (RAPD). Fourteen arbitrary decamers displayed same banding profile within all the micropropagated plants and in vivo explant donor plant. The molecular analysis complemented and compared well and showed genetic stability in the plants regenerated through direct shoot bud differentiation from leaf explants. The gas chromatogram of the extracted oils from in vitro derived plants and the mother stock plant showed similar essential oil profiles. Rapid and high multiplication frequency, molecular, genetic and essential oil content stability ensure the efficacy of the protocol developed for the production of this industrially important aromatic plant.

Ploidy levels in Beta vulgaris (red beet) plant organs and in vitro systems

AbstractThe ploidy levels of the cells in different organs (leaves, petioles and roots) of red beet (Beta vulgaris L.) plants of different ages, as well as of different in vitro systems (transformed hairy roots, calli derived from leaves and rhizogenic calli), were investigated using flow cytometry. Two callus lines with red and yellow phenotypes, derived by mechanical separation of the morphologically heterogeneous rhizogenic callus, were also examined. All investigated samples experienced several cycles of endoreduplication. The older organs exhibited higher levels of polysomaty than the young ones. The highest degree of endoreduplication was found in old petiole tissue and the lowest in the red callus line (cycle values of 1.81 and 0.55, respectively). Interestingly, the callus derived from leaves did not exhibit a 2Cx peak, but was tetraploid, probably due to genetic instability, which may have been caused by prolonged cultivation under in vitro conditions. Red and yellow calli showed significantly lower polysomaty (cycle values of 0.55 and 0.59, respectively) than the primary rhizogenic callus (cycle value of 1.09). The DNA profiles of the two phenotypes differed, possibly reflecting differences in their metabolism.

Comparison of the water-soluble carbohydrate composition and fructan structures of Agave tequilana plants of different ages

Abstract The composition of water-soluble carbohydrates from Agave tequilana plants of 2, 4 and 6½ years were compared by HPLC, HPAEC-PAD, MALDI-TOF-MS and GC–MS. The plants of 2 years exhibited the highest levels of free monosaccharide and low molecular weight fructans (DP 3–DP 6) with potential application as prebiotics. A maximum of fructan polymerisation was achieved at 4 years with mean DP from 3 to 30, then it was decreased at 6½ years with mean DP from 4 to 24. The linkage analysis showed an increase and decrease in the branching degree from 2 to 6½ years with a maximum at 4 years, correlated to changes in t-β- d -Fruf linkages with increased and decreased synthesis of (2→1) and (2→6)-β- d -Fruf as well as 1,6-di-β- d -Fruf linkages.

Caracteristicas anatômicas da casca e produção de látex em plantas de seringueira não enxertadas

As estruturas envolvidas na produção de látex na seringueira são os laticíferos articulados. O objetivo deste estudo foi descrever aspectos anatômicos da casca em seringueiras não enxertadas com quatro, seis e oito anos, visando à seleção de materiais promissores. O material analisado foi obtido através do corte da casca à altura aproximada de 1,50 m do solo, chegando até o xilema da planta. Os cortes transversais foram preparados de acordo com as técnicas usuais de microtécnica vegetal. Os resultados permitem concluir, que a utilização de caracteres anatômicos (diâmetro das células), da espessura da casca e do diâmetro do caule, visando à seleção dos materiais de pés-francos com idades diferentes, apresentaram uma correlação significativa com a produção de látex.

Transcriptomic changes in wind-exposed poplar leaves are dependent on developmental stage

Responses of plant tissue to environmental challenges can vary among different plant parts and among plants of different ages. Investment into defense has been proposed to be influenced by fitness value and/or allocation of available resources. Here we show at first time at transcriptome level that plant defense is non-linear. On very young, expanding, adult and old leaves of Populus nigra plants exposed to air perturbation, we studied the ontogenic trajectory of gene expression changes to such a low-dose factor similar to wind. Although plant responses to mechanical sensation (wind, touch) are described and summarized as thigmomorphogenesis, the knowledge on the molecular background of plant responses to wind is largely incomplete. Our data describe which genes are activated during a ubiquitous and continuous environmental factor such as wind, and based on existing knowledge complement the picture on ongoing processes.

Cytokinin Stimulates Chloroplast Transcription in Detached Barley Leaves

Chloroplasts are among the main targets of cytokinin action in the plant cell. We report here on the activation of transcription by cytokinin as detected by run-on assays with chloroplasts isolated from apical parts of first leaves detached from 9-d-old barley (Hordeum vulgare) seedlings and incubated for 3 h on a 2.2 x 10(-5) m solution of benzyladenine (BA). Northern-blot analysis also detected a BA-induced increase in the accumulation of chloroplast mRNAs. A prerequisite for BA activation of chloroplast transcription was preincubation of leaves for 24 h on water in the light, resulting in a decreased chloroplast transcription and a drastic accumulation of abscisic acid. Cytokinin enhanced the transcription of several chloroplast genes above the initial level measured before BA treatment, and in the case of rrn16 and petD even before preincubation. Cytokinin effects on basal (youngest), middle, and apical (oldest) segments of primary leaves detached from plants of different ages revealed an age dependence of chloroplast gene response to BA. BA-induced stimulation of transcription of rrn16, rrn23, rps4, rps16, rbcL, atpB, and ndhC required light during the period of preincubation and was further enhanced by light during the incubation on BA, whereas activation of transcription of trnEY, rps14, rpl16, matK, petD, and petLG depended on light during both periods. Our data reveal positive and differential effects of cytokinin on the transcription of chloroplast genes that were dependent on light and on the age (developmental stage) of cells and leaves.

Meristem aging is not responsible for age‐related changes in growth and abscisic acid levels in the Mediterranean shrub, Cistus clusii

To obtain new insights into the mechanisms underlying aging in perennials, we measured abscisic acid levels, growth and other stress indicators in leaves of Cistus clusii Dunal plants of different ages grown under Mediterranean field conditions. Recently emerged leaves from 9-year-old plants were compared to those of 1-year-old plants (obtained from cuttings from 9-year-old plants) to evaluate the effects of meristem aging on plant aging. Rooting and successful establishment of the cuttings allowed us to compare the physiology of plants with old meristems, but of different size. Plants obtained from cuttings were rejuvenated, with new leaves displaying a higher leaf area and chlorophyll content, but smaller leaf mass per unit area ratios and endogenous abscisic acid levels than those of 9-year-old plants. A comparative study in 1-, 4- and 9-year-old plants revealed that abscisic acid levels increase during the early stages of plant life (with increases of 90% between 1- and 4-year-old plants), but then remain constant at advanced developmental stages (between 4- and 9-year-old plants). Although leaf biomass was 53% smaller in 9-year-old compared to 4-year-old plants, the dry matter produced per shoot apical meristem was equivalent in both plant groups due to an increased number of leaves per shoot in the former. It is concluded that (i) C. clusii plants maintain the capacity to rejuvenate for several years; (ii) newly emerged leaves accumulate higher amounts of abscisic acid during early stages of plant life, but the levels of this phytohormone later remain constant; and (iii) although plant aging leads to the production of smaller leaves, the amount of biomass produced per shoot apical meristem remains constant at advanced developmental stages.

Tocopherol quinone content of green algae and higher plants revised by a new high-sensitive fluorescence detection method using HPLC – Effects of high light stress and senescence

A rapid, sensitive fluorescence method was applied here for detection of oxidized tocopherol quinones in total plant tissue extracts using HPLC, employing a post-column reduction of these compounds by a Zn column. Using this method, we were able to detect both alpha- and gamma-tocopherol quinones in Chlamydomonas reinhardii with a very high degree of sensitivity. The levels of both compounds increased under high light stress in the presence of pyrazolate in parallel to a decrease in the content of the corresponding tocopherols. The formation of tocopherol quinones from tocopherols was apparently due to their oxidation by singlet oxygen, which is formed in photosystem II under high light stress. alpha-Tocopherol quinone was also detected in a variety of higher plants of different age, and its level was found to increase during senescence in leaves grown under natural conditions. In contrast to alpha-tocopherol quinone, gamma-tocopherol quinone was not found in the higher plant species investigated with the exception of young runner bean leaves, where the levels of both compounds increased dramatically during cold and light stress. Taking advantage of native fluorescence of the reduced alpha-tocopherol quinone (alpha-tocopherol quinol), it can be detected in plant tissue extracts with a high sensitivity. In young runner bean leaves, alpha-tocopherol quinol was found at a level similar to alpha-tocopherol.

Toxicity and Characterization of Cotton Expressing <I>Bacillus thuringiensis</I> Cry1Ac and Cry2Ab2 Proteins for Control of Lepidopteran Pests

Cry1Ac protoxin (the active insecticidal toxin in both Bollgard and Bollgard II cotton [Gossypium hirsutum L.]), and Cry2Ab2 toxin (the second insecticidal toxin in Bollgard II cotton) were bioassayed against five of the primary lepidopteran pests of cotton by using diet incorporation. Cry1Ac was the most toxic to Heliothis virescens (F.) and Pectinophora gossypiella (Saunders), demonstrated good activity against Helicoverpa zea (Boddie), and had negligible toxicity against Spodoptera exigua (Hübner) and Spodoptera frugiperda (J. E. Smith). Cry2Ab2 was the most toxic to P. gossypiella and least toxic to S. frugiperda. Cry2Ab2 was more toxic to S. exigua and S. frugiperda than Cry1Ac. Of the three insect species most sensitive to both Bacillus thuringiensis (Bt) proteins (including H. zea), P. gossypiella was only three-fold less sensitive to Cry2Ab2 than Cry1Ac, whereas H. virescens was 40-fold less sensitive to Cry2Ab2 compared with CrylAc. Cotton plants expressing Cry1Ac only and both Cry1Ac and Cry2Ab2 proteins were characterized for toxicity against H. zea and S.frugiperda larvae in the laboratory and H. zea larvae in an environmental chamber. In no-choice assays on excised squares from plants of different ages, second instar H. zea larvae were controlled by Cry1Ac/Cry2Ab2 cotton with mortality levels of 90% and greater at 5 d compared with 30-80% mortality for Cry1Ac-only cotton, depending on plant age. Similarly, feeding on leaf discs from Cry1Ac/Cry2Ab2 cotton resulted in mortality of second instars of S.frugiperda ranging from 69 to 93%, whereas exposure to Cry1Ac-only cotton yielded 20-69% mortality, depending on plant age. When cotton blooms were infested in situ in an environmental chamber with neonate H. zea larvae previously fed on synthetic diet for 0, 24, or 48 h, 7-d flower abortion levels for Cry1Ac-only cotton were 15, 41, and 63%, respectively, whereas for Cry1Ac/Cry2Ab2 cotton, flower abortion levels were 0, 0, and 5%, respectively. Cry1Ac and Cry2Ab2 concentrations were measured within various cotton tissues of Cry1Ac-only and Cry1Ac/Cry2Ab2 plants, respectively, by using enzyme-linked immunosorbent assay. Terminal leaves significantly expressed the highest, and large leaves, calyx, and bracts expressed significantly the lowest concentrations of Cry1Ac, respectively. Ovules expressed significantly the highest, and terminal leaves, large leaves, bracts, and calyx expressed significantly (P < 0.05) the lowest concentrations of Cry2Ab2. These results help explain the observed differences between Bollgard and Bollgard II mortality against the primary lepidopteran cotton pests, and they may lead to improved scouting and resistance management practices, and to more effective control of these pests with Bt transgenic crops in the future.